Alkaline phosphatase (AP) of E. coli can function as phosphomonoesterase and as a transphosphorylase. Its synthesis is regulated by the cell in response to changes in the phosphate (Pi) concentration of the growth medium. As many as seven genes external to the gene coding for AP (phoA) may control this response. An understanding of the control mechanism and of the functional importance of AP in the cell are the objectives of this project. To study the function of the control genes a cell free system for AP synthesis was developed. Results show that so far only phoB, the gene of positive control, affects cell-free AP synthesis. The constitutive mutations phoR, phoS, phoT, have no effect on the cell-free synthesis suggesting an indirect effect of these gene products on AP synthesis in the cell. Three genes are known to be part of the phosphate (Pi) transport system (PST): phoS, pst, phoT. A dominance test was successfully attempted by using lambda transducing phages: only two of these mutations are recessive to the wild type, while the third failed to complement. It was observed that some of the phoT negative mutants accumulate double mutants uninducibles for AP during anaerobiosis. These have been identified as phoT negative phoB negative. These observations suggest a link between Pi transport, positive control and anaerobiosis. In anaerobiosis the reduced uptake of Pi by phoT negative mutants may not be sufficient for the needs of the cell if Pi is diverted into storage of polyphosphates. This question is being investigated.